1. Field
The disclosed concept relates generally to fuses and, more particularly, to fuses such as, for example, expulsion fuses. The disclosed concept also relates to trip mechanisms for fuses.
2. Background Information
Traditionally, fuses are relatively simple thermal devices. A medium voltage current-limiting fuse, for example, generally includes at least one element (e.g., without limitation, wire) having known electrical resistance and thermal properties matched to an application such that when a predetermined electrical current is supplied, the wire or solder connection melts, thereby triggering the fuse to interrupt the flow of electrical current. In such fuses, this action is the only means to trigger the fuse to interrupt current flow. Accordingly, fuses are generally designed (and correspondingly rated) to allow the flow of an electrical current up to a certain current threshold. Once the current threshold is exceeded, the element of the fuse opens, thereby protecting the power circuit from the overcurrent condition.
Electronically controlled fuse technology has been developed, wherein the flow of electrical current is monitored by a processor, and a fuse/switch combination is employed to interrupt the circuit under certain predetermined conditions (e.g., without limitation, a current overload). Specifically, a high-speed switch is placed in parallel with a traditional current-limiting fuse to shunt the electrical current away from the fuse and through the high-speed switch. When the processor detects the predetermined fault condition, an electronic signal is sent to the high-speed switch to open the switch and transfer all of the current through the fuse. The fuse then interrupts the circuit. There are, however, a number of disadvantages associated with such systems, including the fact that high-speed switches are expensive, which in turn makes such electronically controlled fuses costly to manufacture.
There is, therefore, room for improvement in fuses, and in trip mechanism therefor.